Saccharina japonica and Undaria pinnatifida are the two most commercially important kelps in the world. However, continuous rising seawater temperatures and more frequent marine heatwaves are increasingly threatening the kelp cultivation industry, making it urgent to breed high-quality, heat-tolerant, stress-resistant, and widely adaptable kelp cultivars.
To address this issue, the research team led by Prof. SHAN Tifeng from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) has successfully developed new technique for kelp polyploid breeding. Their findings were published in Journal of Phycology on September 18.
Polyploid breeding, an important strategy in terrestrial crop improvement, has rarely been applied to seaweeds. Previous studies obtained diploid gametophytes from heterozygous sporophytes via apospory, but the resulting gametophytes showed variable sex phenotypes, making it difficult to carry out precise cross to generate triploids.
The researchers obtained a large number of diploid aposporous gametophytes from sporophytes of three origins: selfing of monoicous gametophytes, parthenogenesis of female gametophytes, and cross-fertilization. They generated triploid lines by crossing diploid and haploid gametophytes and found six triploid lines with economic traits superior to the diploid control. In addition, they obtained 5 tetraploid sporophyte lines via selfing or parthenogenesis of diploid gametophytes.
"We expanded the routes to generate diploid gametophytes with clear sex phenotype, and established the new technique for polyploid breeding in Undaria pinnatifida", said Prof. SHAN, corresponding author of the study. "This technique is also applicable to other kelp species because they have a similar life cycle."
They also have established the largest germplasm stock culture collection of Undaria pinnatifida in China, maintaining over 2,000 gametophyte clonal lines. These valuable materials provide ample germplasm resources for triploid breeding of this species.
This study is of great significance for establishing a key polyploid breeding technology system for economically important kelps, laying a foundation for developing triploid cultivars with superior quality, stress tolerance, and wide adaptability.
Morphology of triploid sporophytes. (Image by IOCAS)
(Text by SHAN Tifeng)
Media Contact:
ZHANG Yiyi
Institute of Oceanology
E-mail: zhangyiyi@qdio.ac.cn
(Editor: ZHANG Yiyi)